The Northwestern University laboratory has developed multi-frequency (X, Q, W bands) CW and pulsed ENDOR spectroscopic capabilities into a unique resource that is critical to the collaborative NIH-funded research of the Users Group. Q-band CW ENDOR spectroscopy provides the foundation of this program,. But currently, experiments must be performed on an aged and failing Q-band Varian E-line EPR spectrometer. This must be replaced, and funds are requested for the purchase of a Bruker EMX 13/15 Q-band EP0R spectrometer with Q- band bridge and related equipment. This will be mated to the CW ENDOR apparatus in current use.